The present application is related to interference filters and particularly interference filters incorporating porous valve metals in their construction.
Interference filters, and their use, are well known throughout the electronics industry. In general, interference filters comprise a capacitive component and an inductive component. In the case of a low pass filter, the low frequency resistance through the capacitive component exceeds the low frequency resistance through the inductive component and the signal passes through the inductive component. As the frequency increases the resistance through the inductive component exceeds the resistance through the capacitor and the high frequency signal passes through the capacitive component to ground.
Exemplary devices are described, for example, in U.S. Pat. No. 6,873,518. These devices are limited in their ability to accurately control the onset frequency and they require a large footprint on the circuit board which has become a serious detriment in modern circuitry.
While the devices of the prior art are beneficial there is an ongoing desire to improve the electrical characteristics associated with interference filters while, at the same time, providing a device which is surface mountable thereby minimizing the footprint required for the passive device. Filters meeting these requirements were previously unavailable and are now provided in the instant invention.